Today's questions are very boring. Having never played a convention game nor had campaigns last longer than a month, there is not much to tell.
Favorite convention game: none
Longest campaign played: 1 month
So instead let me talk about how I have started my current world building. Over many years I have had disconnected ideas never used, then when drawing with my kids they took my paper and put a bunch of random dots and told me to do something with them.
So I did. One of the things I added was a location called The Cradle, next to the great barrier nebula.
Then my thought was to make it a place of mystery, and locate some of my various ideas there. While this is where it started, my only focus has been the fantasy setting in The Cradle. A binary star system with 9 habitable planets, makes for a great place for possible spell jamming style adventure and more.